The present invention relates to a method for assembling structural frame members of an image forming apparatus such as an optical device, office automation devices, especially, a copy machine and a laser beam printer (LBP) and, more particularly, to a structure which includes such units as an optical unit, a fixing unit, and a transfer unit arranged in a frame of a main body structure.
Conventionally, there is a widely known method of assembling a plate metal structure, such as a main body frame of an image forming apparatus, e.g., an optical device, a copy machine, and a LBP, requiring certain precision in which plate metal members consisting the plate metal structure are assembled in position using an exclusive assembly set-up member and, subsequently, the metal members are fixed to each other with screws or by welding.
FIG. 16 is a figure showing a frame of a main body structure of an image forming apparatus, such as a copy machine.
In a conventional structure, when supporting members 166, 164, and 162 for supporting an optical unit, a transfer unit, and a fixing unit provided inside of side plate members 168 and 170, and not-shown bottom and top plate members are assembled and combined by screws, each aforesaid member is set in its position by a position deciding means, such as a cylinder unit 154 on an assembly set-up member 150, fixed in its position by a clamp 152, and then combined.
More specifically, each member is set and kept in its position on the assembly set-up member 150, the supporting members are then combined by tightening screws 172 (about 40 screws, and the number depends upon the type of an apparatus). Then, the completed main body frame is taken off from the assembly set-up member 150.
Thereby, the main body frame, and the like, of the image forming apparatus can be assembled in a high degree of tolerance.
However, there are the following problems in the aforesaid conventional method when productivity is concerned.
(1) Since the assembly set-up member is a large, complicated, exclusive and special member, the cost for equipment is high.
(2) When an assembling system is automated by using a screw-tightening device or the like, it consumes extra time to change the assembly set-up members for the assembling system, thus reducing productivity.
(3) When the aforesaid main body frame of the image forming apparatus is to be assembled, the tolerance degree of adjusting the relative position (distance) between the main body frame and each unit, e.g., especially an optical unit, relates to the clearness and resolution of a focused image of an original image formed on an electrostatic drum, and affects the quality of the printed image.
(4) Regarding the transfer unit and the fixing unit, when an image is transferred from an electrostatic drum to a transfer paper sheet, it is necessary to accomplish adjustment of the distances from a reference position of the electrostatic drum (the central axis of the electrostatic drum) to reference positions of each unit in a high degree of tolerance.